JP2919817B2 - Manufacturing method of printed wiring board - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a printed wiring board, and more particularly to a method for forming a conductive pattern on the printed wiring board at a relatively low cost and quickly by a so-called additive process.

[0002]

2. Description of the Related Art In recent years, with the advance of electronic industry technology, electronic devices have been reduced in size and speed. Accordingly, printed wiring boards and wiring boards on which LSIs are mounted have been required to have higher density and higher reliability by fine patterns.

[0003] As a method of responding to such a demand,
Recently, a so-called additive process for forming a conductor pattern by electroless plating has been proposed. By the way, since the additive process is a method of performing electroless copper plating, it requires cost and time, and further has the following problems. That is, since the plating solution used is strongly basic, there is a need for a plating resist that can withstand such a plating solution for a long time. It is to be high.

As a means for solving such a problem, a conventional method for forming a conductor pattern by electrolytic plating includes, for example, (1) First, a through hole for a through hole is provided in a copper-clad laminate, A method for removing copper between patterns by performing electroless plating on the entire surface, then coating a plating resist, and then electroplating to form a conductor pattern, and then peeling and removing the plating resist and performing etching. , (2) apply electroless plating to the surface of the insulating plate on which the adhesive layer for electroless plating is formed, then form a plating resist, form a conductor pattern by electrolytic plating, and then remove and remove the plating resist A method of removing the copper between the patterns by performing etching after that has been proposed.

[0005]

However, these methods have many problems, such as a large number of steps, a complicated process, an etching process, which makes it difficult to achieve a high density, and a poor pattern accuracy. Yes, it was a method that eventually reduced the benefits of the additive process. As described above, it has been difficult for the conventional method to form a conductor pattern by electrolytic plating without impairing the advantages of the additive process.

An object of the present invention is to complete a method of manufacturing a printed wiring board which can overcome the above-mentioned problems of the prior art.

[0007]

In order to achieve the above-mentioned object, the present inventors first form a thin pad as a lead for electrolytic plating together with a part of a conductor pattern by performing electroless plating. I do. Then, a method was developed in which a current was passed through the pad formed at that time to perform electrolytic plating, thereby forming a final conductive pattern having a predetermined thickness.

That is, the present invention provides at least the following:
Steps (a) to (c), that is, (a) forming an adhesive layer for electroless plating on a substrate, then forming a plating resist, and then applying electroless plating to form a conductor pattern at the same time a part of the building shape of a step of forming a pad as an electrolytic plating leads into the substrate, path obtained by electroless plating in the (b) step (a)
By performing electroless plating through the head, the step of the already formed thin the conductor pattern by thickening of predetermined thickness conductive pattern, (c) a above the pad, removed by means of punching or etching (B ) a step of insulating between the conductor patterns formed in the step (b ).

In the above step, it is preferable that each of the part of the thin conductive pattern formed by electroless plating and the lead for electrolytic plating has a thickness of 2 μm or more.

[0010] The adhesive layer for electroless plating is formed by heating a heat-resistant fine powder which has been cured in advance and is soluble in an oxidizing agent. After having been cured,
It is preferably formed by treating with an oxidizing agent.

[0011]

Detailed Description of the Invention The present onset Akira, on a substrate (laminate)
First forming an adhesive layer for electroless plating, then disposed plating resist used during electroplating, followed with thin conductor pattern building form a part of the conductor pattern, the conductor pattern electrically electroplating energizing For lead
This is a method of forming a pad as above and performing electroless plating through this pad .

That is, according to the present invention, by applying a current to the pad and performing electrolytic plating, a predetermined film is further formed on the conductive pattern already formed in a thin film (膜 2 μm) by electroless plating. Thickness (about 10μm ~ 35μm)
To form a thickened conductor pattern. Thereafter, insulation between the conductor pattern by removing such pads (see FIG. 1 (f), the FIG. 2 (f), the FIG. 3 (g)).

In such a manufacturing method, since most of the conductor patterns are formed by electrolytic plating, the conductor patterns can be formed at a lower level than in the conventional case where all of the conductor patterns are formed using only electroless plating. It can be formed at low cost and in a short time. Furthermore, in this method, since there is no need to consider the base resistance of the plating resist so much, there is an advantage that a low-cost plating resist can be used.

It is desirable that the thickness of each of the thin conductor pattern formed in advance by electroless plating and the thin lead for electrolytic plating be 2 μm or more. The reason for this is that if the thickness of the electroless plating film is less than 2 μm, sufficient electrical conduction cannot be achieved, and good electrolytic plating cannot be performed.

The electroless plating may be any of electroless copper plating, electroless nickel plating, electroless tin plating, electroless gold plating, and electroless silver plating. Electroless copper plating is optimal.

The electrolytic plating may be any of electrolytic copper plating, electrolytic nickel plating, electrolytic tin plating, electrolytic gold plating, and electrolytic silver plating.
Of these, electrolytic copper plating is a preferable method.

It should be noted that, after performing the above-described electrolytic plating, a different type of electrolytic plating may be performed, or a process of coating solder may be performed. In particular, by performing electrolytic nickel plating and electrolytic gold plating, respectively, after performing electrolytic copper plating, it is possible to form a conductor pattern having good adhesion to gold wires used in a COB (chip-on-board) substrate or the like. .

The lead for electrolytic plating according to the present invention comprises:
Inside the board, that is, inside the lead wire
This is a pad formed at an intermediate position between the lead wire and the wiring pattern . The reason why the lead for electrolytic plating has such a shape is to minimize the loss of the effective area of the substrate due to the lead for electrolytic plating and to facilitate the removal of the lead for electrolytic plating. Before Symbol pads, electrical connection between the conductor pattern is obtained by a lead wire, the
In the present invention, when performing electrolytic plating, a current may be passed through a pad which is a lead for electrolytic plating.

Next, in the present invention, as a method of insulating the lead for electrolytic plating and the conductor pattern, a method of punching out a pad as the lead for electrolytic plating by punching or dissolving and peeling by etching is used. .

Next, the adhesive layer for electroless plating used in the present invention is made of a heat-resistant fine powder which has been cured beforehand and which is soluble in an oxidizing agent. It is desirable that the resin is formed by curing a resin dispersed in a heat-resistant resin that becomes soluble and then treating the resin with an oxidizing agent. For example, a mixture of a heat-resistant resin particle having an average particle size of 2 to 10 μm and a heat-resistant resin fine powder having an average particle size of 2 μm or less in a heat-resistant resin having poor solubility in an oxidizing agent, and an average particle size of 2 to 10 μm Heat-resistant resin fine powder having an average particle size of 2 μm or less or an average particle size of 2
pseudo particles obtained by adhering at least one kind of inorganic fine powder having a particle diameter of not more than μm, or at least one kind of particles selected from aggregated particles having an average particle diameter of 2 to 10 μm; It is preferable that the adhesive layer is formed by curing a material containing heat-resistant particles soluble in the agent, and then treating with an oxidizing agent. This adhesive layer has a surface having a large number of anchors formed thereon due to the difference in solubility with respect to the oxidizing agent, and can improve the adhesion strength of the plating film such as peel strength and pull strength.

The oxidizing agent used for forming the adhesive layer may be chromic acid, chromate, permanganate,
Ozone or the like can be used, and as the resin constituting the heat-resistant particles, at least one selected from an epoxy resin, a polyester resin, and a bismaleimide-triazine resin can be used. However, epoxy resins are preferred. In addition, as the inorganic fine powder that is soluble in an oxidizing agent, for example, calcium carbonate is used.

[0022]

【Example】

(Example 1) (1) Epoxy resin particles (Torepearl EP-, manufactured by Toray)
B, average particle size 0.5 μm) was charged into a hot air drier and 180
Heat treatment was performed at 3 ° C. for 3 hours to cause cohesive bonding. The cohesively bonded epoxy resin particles were dispersed in acetone, crushed in a ball mill for 5 hours, and then classified using an air classifier to prepare epoxy resin aggregate particles. The epoxy resin aggregated particles had an average particle size of about 3.5 μm, and about 68% by weight was in a range of ± 2 μm around the average particle size. (2) Epoxy resin pseudo particles 50 prepared in the step (1)
Parts by weight, 60 parts by weight of phenol novolak type epoxy resin (trade name: E-154, manufactured by Yuka Shell), bisphenol A
Butyl carbitol was added to a resin consisting of 40 parts by weight of a mold resin (manufactured by Yuka Shell, E-1001) and 4 parts by weight of an imidazole curing agent (manufactured by Shikoku Chemicals, 2P4MHZ) to prepare an adhesive solution. (3) After applying the adhesive solution obtained in the above step (2) to a glass polyimide substrate 1 (manufactured by Toshiba Chemical Co., Ltd., trade name: Toshiba Dulite Laminate-EL), the coating is applied at 100 ° C. for 1 hour and then at 150 ° C. For 5 hours to form an adhesive layer 2 having a thickness of 20 μm. (4) The substrate 1 on which the adhesive layer 2 obtained in the above step (3) is formed is treated with
C. for 15 minutes to roughen the surface of the adhesive layer 2,
It was immersed in a neutralization solution (manufactured by Shipley, trade name: PN-950) and washed with water. (5) A palladium catalyst (manufactured by Shipley, trade name: Cataposit 44) is applied to the substrate 1 having a roughened surface of the adhesive layer 2 obtained in the above step (4), so that the surface of the adhesive layer 2 is formed. Activated. (6) Laminate a photosensitive dry film on the substrate 1 and expose it to ultraviolet light through a mask film on which a desired conductor circuit pattern and electrolytic plating leads are drawn,
Image burned. Subsequently, the resist was developed with a 5% sodium carbonate solution to form a plating resist 3. (7) Immersion in an electroless copper plating solution having the composition shown in Table 1 for 30 minutes, electroless plating and flash plating (thin plating) to form a conductor pattern having a thickness of 3 μm. A portion 4 and a pad 9 serving as a lead for electroless plating were formed at the center of the substrate 1.

[0023]

[Table 1]

(8) Next, a current was applied to the pad 9 for electrolytic plating, and electrolytic copper plating was performed under the conditions shown in Table 2 to form a conductive pattern 8 having a thickness of 35 μm.

[0025]

[Table 2]

(9) After buffing and smoothing the substrate surface, the electrolytic plating pad 9 is removed by cutting using a drill, and the conductor pattern is removed as shown in FIG. 1 (f).
8 were insulated to obtain a printed wiring board.

Example 2 (1) 60 parts by weight of a phenol novolak type epoxy resin (manufactured by Yuka Shell, E-154), 40 parts by weight of a bisphenol A type epoxy resin (E-1001 manufactured by Yuka Shell), imidazole cured 4 parts by weight of agent (2P4MHZ, manufactured by Shikoku Chemicals), coarse particles for anchor formation, and epoxy resin powder as a fine powder (Toray, Trepearl EP-B, average particle size: 3.9 μm)
10 parts by weight and epoxy resin (Toray, Trepal EP
-B, average particle size 0.5 μm) To 25 parts by weight of butyl carbitol was added to prepare an adhesive solution. (2) After forming an adhesive layer on both sides of the substrate 1 by the same method as in the step (3) of the first embodiment, the roughening of the adhesive layer 2 is performed by the method shown in the step (4) of the first embodiment. Then, a roughened surface 2 'was formed. (3) A through hole 10 for forming a through hole was formed by a drill. (4) A palladium catalyst (trade name: Cataposit 44, manufactured by Shipley Co., Ltd.) was applied to the substrate 1 to activate the roughened surface 2 ′ of the adhesive layer 2. (5) The plating resist 3 is formed on both sides of the substrate 1 by the method of the step (6) of the first embodiment.
According to the method (7), a 3 μm-thick electroless copper plating process was performed to form the conductor pattern 4, the lead wire 5, and the pad 9 as a lead for electrolytic plating. (6) An electric current was applied to the lead pad 9 and electrolytic copper plating was performed under the conditions shown in Table 2 to form a conductive pattern 8 and a through hole 11 having a thickness of 30 μm. (7) The pad 9 is punched and removed by punching, and FIG.
As shown in (d), the conductor patterns 8 were insulated from each other to obtain a printed wiring board.

Example 3 This example is basically the same as Example 1, except that a photosensitive dry film (manufactured by DuPont, trade name: Liston 105
By laminating 1) and performing exposure and development, an etching resist 12 is formed in a portion other than the pad 9;
The electrolytic plating lead pad 9 is dissolved and removed with a cupric chloride etching solution, and as shown in FIG.
Insulated between them. Then, the etching resist was peeled off with methylene chloride to obtain a printed wiring board.

With respect to the results of the operation, Table 3 shows the time required for forming the conductor pattern for the printed wiring boards manufactured by the methods described in Examples 1 to 3 above. For comparison, a case where an equivalent printed wiring board is manufactured by a conventional additive method is also shown. Further, the pattern accuracy (deviation from the design value of the pattern width) of the printed wiring boards obtained in Examples 1 to 3 was about ± 3 μm, and the same pattern accuracy as the additive method was obtained. Incidentally, the pattern accuracy of the subtractive method is ± (20 to 40) μm, and the method described in the prior art (1) or (2) is ± (10 to 2).
0) μm, and it was found that the printed wiring board obtained in the steps of each of the above-described examples had better pattern accuracy than the conventional technology. In each of the examples, the manufacturing cost per 1 m ^{2 of} the printed wiring board could be reduced by about 10 to 15% as compared with the conventional additive method.

[0030]

[Table 3]

[0031]

As described above, according to the present invention, a high-density wiring board can be easily manufactured with high reliability.
In addition, it is effective to manufacture a product with high pattern accuracy at low cost.

[Brief description of the drawings]

FIGS. 1A to 1F are explanatory diagrams of a manufacturing process in Example 1. FIG.

FIGS. 2A to 2F are explanatory diagrams of a manufacturing process in Example 2. FIGS.

3 (a) to 3 (g) are explanatory diagrams of a manufacturing process in Example 3. FIG.

[Description of Signs] 1 Substrate 2 Adhesive layer 2 'Roughened surface 3 Plating resist 4 Electroless plating conductor pattern 5 Lead wire 7 Current input terminal 8 Conductor pattern 9 Electroplating pad (lead for electrolytic plating) 10 Through hole Through hole 11 Through hole 12 Etching resist

Continued on the front page (58) Fields surveyed (Int.Cl. ⁶ , DB name) H05K 3/10-3/26 H05K 3/38

Claims (3)

(57) [Claims] In the manufacture of a printed wiring board, (a) an adhesive layer for electroless plating is first formed on a substrate, a plating resist is formed, and then the electroless plating is performed. at the same time a part of the building shape of a step of forming a pad as an electrolytic plating leads into the substrate, path obtained by electroless plating in the (b) step (a)
By performing electroless plating through the head, the step of the already formed thin the conductor pattern by thickening of predetermined thickness conductive pattern, (c) a above the pad, removed by means of punching or etching (B ) a step of insulating between the conductor patterns formed in the step (b ). 2. In the step (a), a part of a thin conductor pattern formed by electroless plating and a lead for electrolytic plating are each made to have a thickness of 2 μm or more. The production method described in 1. 3. The adhesive layer for electroless plating is formed by hardening a heat-resistant resin fine powder which has been cured in advance and is soluble in an oxidizing agent. The production method according to claim 1, wherein the composition is formed by subjecting a resin dispersed in a conductive resin to a curing treatment, and then treating with an oxidizing agent.